School of Health Sciences, University of Southampton, Southampton, UK. Department Care I, Musculoskeletal System & Neurology, Dutch National Health Care Institute, Diemen, The Netherlands. EULAR Standing Committee of People with Arthritis/Rheumatism in Europe (PARE), Zurich, Switzerland. EULAR Young PARE, Zurich, Switzerland. Slovak League Against Rheumatism, Piestany, Slovakia. Medicine for Older People, University Hospital Southampton NHS Foundation Trust, Southampton, UK. Department of Rheumatology, Aarhus University Hospital, Arrhus, Denmark. INSERM U1153, Paris Descartes University, Reference Center for Genetic Bone Diseases - Department of Rheumatology, Cochin Hospital, Paris, France. Department of Orthopedics and Trauma-Surgery, Medical University of Vienna, Vienna, Austria. MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton, UK. Rehabilitation, Physical Medicine and Rheumatology, 'Victor Babes' University of Medicine and Pharmacy, Timisoara, Timisoara, Romania. Section for Outcomes Research, Centre for Medical Statistics, Informatics, and Intelligent Systems, Medical University of Vienna, Vienna, Austria. Department of Rheumatology, VU University Medical Centre Amsterdam, Amsterdam, Noord-Holland, The Netherlands. Centre for Biomedical Research, Department of Biomedical Sciences and Medicine, University of Algarve, Faro, Portugal. Department of Balneology, Rehabilitation and Rheumatology, 'Victor Babes' University of Medicine and Pharmacy, Timisoara, Timisoara, Romania. Internal Medicine 3, Division of Rheumatology, Medical University Vienna, Vienna, Austria. Trauma & Orthopaedics, University Hospital Southampton NHS Foundation Trust, Southampton, UK. Day Hospital, Alicante General and university Hospital, Alicante, Spain. Section for Outcomes Research, Centre for Medical Statistics, Informatics, and Intelligent Systems, Medical University of Vienna, Vienna, Austria tanja.stamm@meduniwien.ac.at. Ludwig Boltzmann Institute Arthritis and Rehabilitation, Vienna, Austria.